Indoor or “gym” climbing on artificial structures has evolved from the traditional outdoor sport of rock climbing where climbers ascend natural boulders and rock faces. The significant increase in the number of climbing gyms is largely attributed to their convenience, safety, and proximity to residential areas.
The walls at indoor climbing gyms are usually built from prefabricated fake-rock panels or textured plywood sheets that have regularly spaced holes and are attached to a metal or wood framework inside the gym. The walls are attached to the building's structure at both the base and the top so that they are stable and don't move or flex. While most gym walls are vertical, some walls have horizontal overhangs or sections that are other than 90° from the floor. Indoor climbing walls range in height from 10 to 50 feet.
Climbing holds are made of resin poured into molds of varying shapes and sizes from tiny edges to giant hand-sized buckets. The holds are bolted onto the wall's threaded holes using cap end hex bolts to provide support and/or a gripping place for the climber to ascend or traverse the wall.
With the holds attached to the wall, climbing gyms often hire designers to select a subset of the holds and collectively define this group as a ‘route’. Routes are assigned a degree of difficulty from a scale of commonly understood and agreed upon subjective ratings. Climbers use route ratings to gauge their progress and compete against other climbers.
To designate a route, climbing gyms will use homogeneously colored holds, distinctly colored tape, or chalk marks. However, each of these methods has its drawbacks: buying same color holds for each route is prohibitively expensive, inflexible, and does not allow for overlapping routes; tape tends to peel off; and chalk is easily erased when climbers rub against the marks. Furthermore, each of these methods are static and require human interaction to set or alter a route's pattern.
Another issue with tradition indoor climbing routes is that when compared to other leisure activities, they can be boring. Without an interactive component, or game mechanic, climbers often tire of ‘climbing plastic’. This problem is multiplied on home climbing walls that offer fewer routes for the climber to use. Moreover, the lack of interactivity does not allow the climber to improve their technique by providing feedback on their climbing.